It seems like the 7BG set + Uranium and the MIC Wonder is the way to go to afford the upkeep on a large navy and arsenal.
Magic 7 Set:
Aluminum, Marble, Iron, Lumber, Wheat, Fish, Rubber, Coal, Oil, Lead, Gold
Extra Resources: Uranium
Bonus Resources: Construction, Steel, Asphalt, Automobiles, Scholars, Microchips, Radiation Cleanup
Rough math says the naval upkeep will be -38% with this set.
The Mining Industry Consortium Wonder should help bring up the bottom line.
Can someone good with math say how this set-up will compare to the usual Agro and Industrial trade groups if you have +50 ships?